Question

Identify the reagents for all three steps. Draw the structures of organic compounds A and B. Omit byproducts.

Identify the reagents for all three steps. Draw the structures of organic compounds A and B. Omit byproducts.

Reagents given:

- Mg

- 1. ethylene oxide 2. H3O+

- PCC

- 1. CH3CO3H 2. H2O

- H2, Pt

- 1. O3 2. Zn, H2O

- 1. CH3MgBr 2. H3O+

- 1. O3 2. H2O2

Answer 1

Concepts and reason

This problem is based on preparation of an aromatic aldehyde, starting from an aryl halide.

Aldehydes are prepared generally from oxidation of alcohols which can be prepared from an alkyl or aryl halide by Grignard reaction.

Grignard reaction is an important reaction in which an organomagnesium compound called a Grignard reagent acts as a nucleophile that react with carbon based electrophiles such as, aldehydes, ketones, epoxides and esters, followed by hydrolysis with aqueous acid to form new carbon-carbon bonds.

Pyridinium chlorochromate is a reagent used for the oxidation of alcohols to form carbonyl compounds.

Fundamentals

One of an approach to synthesise aldehyde from an alkyl halide is to convert the alkyl halide to an alcohol using Grignard reaction, and then oxidize the alcohol to aldehyde.Grignard reagent is an organomagnesium compound prepared from an alkyl or aryl halide by its reaction with magnesium metal.

The Grignard reagent when treated with ethylene oxide forms a primary alcohol with two more carbon atoms.

A primary alcohol is oxidized to an aldehyde by mild oxidation with PCC

(1)

The reaction of aryl halide with magnesium is as follows:

(2)

The reaction of compound A is as follows:

(3)

The reaction of compound B with PCC is as follows:

Ans: Part 1

The reagent 1 and product A is as follows:

Part 2

The reagent 2 and compound B is as follows:

Part 3

The Reagent 3 is PCC.

Answer 2

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